• Learn Regular Expressions with simple, interactive exercises
• An online tool to learn, build, & test Regular Expressions
• An Online tool that lets you enter your own text and regular expressions to see what matches

Regular expressions (sometimes referred to as RegEx) is an incredibly powerful tool that is used to define string patterns for "find" or "find and replace" operations on strings, or for input validation. Regular Expressions are used in search engines, in search and replace dialogs of word processors and text editors, and text-processing Linux utilities such as sed and awk. They are supported in many programming languages, including Python, R, Perl, Java, and others.